JP2006150699A - Printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing device which has solved the problem that the fluctuation or the like of an image recording position on a sheet of paper by enabling a relative position of a plurality of sheets of the paper on a paper carrying path to be accurately detected. <P>SOLUTION: Respective carrying rollers and platen rollers on the paper carrying path are driven by a stepping motor. At the same time, the detection contents of all sensors on the paper carrying path are simultaneously taken in and stored in a memory after the driving of its one step, and the existence/absence of the paper at the positions of respective sensors is read by referring to the contents of the memory until the steps of the stepping motor progress. The stepping motion of the stepping motor and the reading of the sensors are performed by an interrupting process by a timer interruption. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printing apparatus that conveys a sheet along a sheet conveyance path and performs image recording.

For example, many proposals have been made for thermal printers that record images by bringing a thermal head into contact with a thermal recording material. Also, a certain type of thermal printer, for example, a so-called rewritable printing apparatus that performs image recording using a color-forming reversible thermosensitive recording material (for example, see Patent Document 1) using a leuco dye and a reversible developer. In addition to performing image recording with a thermal head, the image can be erased using a heat roller (see, for example, Patent Document 2).
JP 2004-106308 A JP 2002-331697 A

  Thus, in a printing apparatus that performs image recording by sequentially performing processing at a predetermined position on the paper transport while transporting the paper along the paper transport path, each of the papers is transported when a plurality of paper is sequentially transported to the paper transport path. In order to perform accurate processing at a predetermined position for the paper and to determine where the fault occurred when a paper jam occurs, it is necessary to accurately determine where each paper is on the transport path. It needs to be detected.

  However, in the conventional printing apparatus, a plurality of sensors are arranged to detect the presence / absence of paper at a plurality of locations on the paper transport path, but the detection results of these sensors are sequentially read. As the transport speed increases, the paper travel distance increases in the time required to read the detection results of all sensors in a single cycle, making it impossible to accurately detect the relative positional relationship between each sensor and each paper. was there.

  In addition, since the sheet conveyance timing and the detection timing of the presence / absence of the sheet at each point on the sheet conveyance path by each sensor are substantially asynchronous, the image recording on the sheet is detected after detecting that the sheet has reached a predetermined position. When processing is performed, there is a problem that the image recording position on the paper varies (displaces).

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a printing apparatus that can accurately detect the relative positions of a plurality of sheets on a sheet conveyance path and solves the above-described problems.

  (1) A printing apparatus according to the present invention includes a sheet conveying unit that conveys a sheet to a sheet conveying path by step driving of a stepping motor, an image recording unit that records an image on the sheet conveyed by the sheet conveying unit, and the sheet A sensor for detecting presence / absence of paper, disposed at a plurality of predetermined positions on the conveyance path, and a sensor for simultaneously capturing the contents detected by the plurality of sensors and storing them in the memory after the step driving for each step driving of the stepping motor. Until advancing the step of the stepping motor, state acquisition means and paper processing means for reading the presence or absence of paper at the position of the sensor with reference to the contents of the memory and performing processing according to the position of the paper It is characterized by having prepared.

  (2) Further, in the printing apparatus of the present invention, the paper transport unit and the sensor state acquisition unit are used as an execution unit of an interrupt processing program by the CPU, and the paper processing unit is a program other than the interrupt processing program by the CPU. It is characterized as an execution means.

  (1) After every step driving of the stepping motor, the detected contents of the plurality of sensors are simultaneously fetched and stored in a memory, and the contents of each sensor are referred to until the step of the stepping motor is advanced. By reading the presence / absence of paper at the position, the paper is not transported while sequentially reading the detection results of the sensors on the paper transport path, and the paper is sequentially transported onto the paper transport path. In this case, it is possible to accurately detect the relative positions of a plurality of sheets on the sheet conveyance path.

  (2) The paper processing is performed by executing a program of the CPU, and the sensor state acquisition unit captures the detection contents of each sensor by interrupt processing at the step driving timing of the stepping motor. The sheet conveyance and the detection by the sensor can be performed in parallel while performing processing according to the position of the sheet on the sheet conveyance path.

  FIG. 2 is a top view showing an internal configuration of the printing apparatus 100 according to the embodiment of the present invention. FIG. 1 is a cross-sectional view taken along line AA in FIG.

  On the right side of the printing apparatus 100 in FIGS. 1 and 2, an elevating table 14 on which a large amount of paper is placed, and a separate paper feed tray 16 are provided. The sheet placed on the lifting table 14 is brought into contact with the pickup roller 9 at the left end of the uppermost sheet in the drawing when the lifting table 14 is raised. A clutch 19 is provided on the drive shaft of the pickup roller 9, and the pickup roller 9 rotates rightward in FIG. Thus, the paper is conveyed in the left direction in the figure. Since the paper feed roller 6 rotates in the right direction in the figure, the fed paper is conveyed as it is in the left direction.

  A clutch is provided on the drive shaft of the registration roller 21, and the leading end (left end in FIG. 1) of the fed paper comes into contact with the registration roller 21 when the clutch is off. Thereafter, when the clutch is turned on, the registration roller 21 rotates in the left direction and the sheet is conveyed in the left direction in the drawing.

  Similarly, the leading end (left end in the figure) of the uppermost sheet of the sheets placed on the sheet feeding tray 16 contacts the pickup roller 8. A clutch 18 is provided on the drive shaft of the pickup roller 8, and when the clutch 18 is in an on state, the pickup roller 8 rotates in the right direction in FIG. 1, and the sheet is conveyed in the left direction in the drawing. Since the paper feed roller 7 rotates in the right direction in the figure, the fed paper is conveyed in the left direction. A clutch is provided on the drive shaft of the registration roller 20, and the leading edge of the fed paper comes into contact with the registration roller 20 when the clutch is off. Thereafter, when the clutch is turned on, the registration roller 20 rotates in the left direction, and the sheet is conveyed in the left direction in the drawing.

  On the paper transport path, an R / W unit 5 that reads and writes a non-contact IC tag is disposed between the transport roller 13 and the transport roller 22. A clutch 15 is provided on the drive shaft of the transport roller 13, and when the R / W unit 5 reaches a position where the R / W unit 5 can read and write with respect to the non-contact IC tag built in the paper being transported, the clutch of the transport roller 13 By turning off 15, the paper is stopped in that state. When the sheet is stopped, the R / W unit 5 reads / writes data from / to the non-contact IC tag. Thereafter, the sheet is conveyed by turning on the clutch 15 of the conveying roller 13. The transport roller 22 transports the paper forward (leftward in the figure).

  A cleaning roller 4 and a platen roller 12 as a driving roller are provided in front of the conveying roller 22, and when the sheet passes between the cleaning roller 4 and the platen roller 12, the cleaning roller 4 is an upper surface of the sheet. Remove dust adhering to the (recording surface).

  A heat roller 3 and a platen roller 11 which is a driving roller facing the heat roller 3 are arranged in front of the cleaning roller 4 to constitute an image erasing unit. When the sheet passes between the heat roller 3 and the platen roller 11, the sheet is raised to a predetermined temperature.

  In front of the heat roller 3, cooling fans 2 and 2 for blowing air to the front and back surfaces of the paper are arranged above and below the paper transport path to constitute a cooling unit. The upper and lower cooling fans 2 and 2 gradually lower the temperature of the paper conveyed between them. This erases the image recorded on the paper.

  Further downstream of the cooling unit by the cooling fans 2 and 2, a platen roller 10 that sandwiches the paper between the thermal head 1 and the thermal head 1 is arranged to constitute an image recording unit. When the leading edge of the paper reaches the lower part of the thermal head 1, the thermal head 1 descends, contacts the recording surface of the paper, and records an image by driving the thermal head as the paper is transported.

  Conveying rollers 24 and 25 and a normal paper discharge unit 40 are provided further downstream from the position of the thermal head 1, and the image-recorded paper is conveyed and discharged to the normal paper discharge unit 40.

  Further, an abnormal paper discharge unit 50 is provided between the conveying roller 22 and the platen roller 12 to drop the abnormal paper downward by the flapper and discharge it.

  FIG. 3 is a diagram showing the relationship between the paper detection sensor on the paper transport path and the paper being transported. (A) is the whole block diagram, (B) is the elements on larger scale of (A). The sheet 60 is sequentially conveyed in the order of the registration roller 21, the conveyance rollers 13 and 22, the platen rollers 12 and 11, the conveyance roller 23, the platen roller 10, and the conveyance rollers 24 and 25. Sensors 80a to 80h for detecting the presence or absence of paper are disposed between these transport rollers. In this example, a plurality of sheets 60a, 60b, 60c, and 60d exist on the sheet conveyance path. These sheets are conveyed in the direction indicated by the arrow M. These sensors 80a to 80h are transmissive optical sensors, and detect the presence or absence of a sheet at that position depending on whether or not the position of these sensors interrupts the sheet.

  In each step along the paper transport path, a predetermined process is performed according to the position of the paper transported on the paper transport path. FIG. 4 shows an example of a processing procedure in the image recording unit. When the leading edge of the paper 60c reaches the sensor 80f, the number of steps of the stepping motor until the thermal head 1 starts to descend is counted. When the predetermined number of steps are counted and the state shown in FIG. 4B is reached, the thermal head 1 starts to descend at that time, and a certain margin is provided from the leading edge of the paper 60c as shown in FIG. By contacting the secured position and driving the thermal head 1 along with the conveyance of the paper 60c, the leading edge margin is secured as shown in (D), and then an image is recorded on the recording surface. Thereafter, as shown in (E), immediately after the trailing edge of the sheet 60c passes the sensor 80f, the number of steps until the distance from the trailing edge of the sheet 60c to the thermal head 1 becomes the distance of the end margin is counted. When the state shown in (F) is reached, the thermal head 1 starts to rise. Thereafter, as shown in (G), the paper 60c is conveyed to the next process.

  Thus, in order to execute processing according to the position of the sheet on the sheet conveyance path, the timing relationship between sheet conveyance and position detection is important.

  FIG. 5 shows an arrangement example of the sensors on the plane with respect to the paper transport path. In the example of (A), the sensors (80b, 80b ′), (80c, 80c ′), (80d, 80d ′), (80e, 80e) are paired in pairs in the direction perpendicular to the paper transport direction. ′) Is arranged. With such an arrangement, for example, when the sheet is conveyed obliquely as in the sheet 60b in the figure, one of the paired sensors (sensor 80d 'in this example) detects the sheet first. Subsequently, the sensor 80d detects the sheet, and the detection timing is shifted. By detecting this deviation, it is possible to detect the skew of the sheet, and according to the skew, for example, a process of correcting the tilt of the recorded image can be performed.

  In the example shown in FIG. 5B, a plurality of sensors 80b, 80c, 80d, and 80e are arranged in a staggered pattern along the paper transport direction. Even with such a sensor arrangement, when the paper 60b, 60a, etc. are conveyed without being skewed, which sensor is at which timing at which timing based on the relationship between the number of steps of the stepping motor and the sensor interval. Since it is known in advance whether the leading edge or the trailing edge is to be detected, whether or not the sheet is skewed and the degree of skew are detected based on the deviation from the timing.

FIG. 6 is a block diagram of the control unit of the printing apparatus 100. The control circuit 70 performs the following controls.
A drive signal is output to the motor 17 of the lifting table 14 via the drive unit 75.
A driving signal is output to the clutches 18 and 19 of the pickup roller via driving units 77 and 78, respectively.
A drive signal is output via the drive unit 76 to the flapper 52 that drops and discharges abnormal paper in the direction of the abnormal paper discharge unit 50.
A drive signal is output via the drive unit 74 to the clutch 15 of the R / W unit.
The R / W unit 5 reads / writes data from / to the non-contact IC tag 61 built in the paper.
The heater of the heat roller 3 is controlled via the drive unit 73.
A drive signal is output to the thermal head elevating motor 26 via the drive unit 72.
A drive signal is output to the thermal head 1 via the drive unit 71.
Read the operation content of the operation unit 79 such as a key switch.
The detection signals of various sensors 80 such as a sensor for detecting the presence or absence of paper at a plurality of positions on the paper conveyance path and a sensor for detecting the temperature of the heat roller 3 are read.
Data is input / output to / from the host computer 101 via the interface 90.
A drive signal is output to the stepping motor 33 via the drive unit 85.

Next, the entire processing procedure of the control circuit 70 shown in FIG. 6 will be described with reference to FIG.
FIG. 7 is a flowchart showing a series of flows under the control of the control circuit 70 from when a sheet is fed to when it is discharged. First, one of the clutches 18 or 19 of the pickup roller 8 or 9 is turned on to feed the paper and start conveying (S1). If it is detected that the sheet has reached the R / W unit 5 according to the reading result of the sensor for detecting the position of the sheet on the sheet conveyance path, the clutch 15 of the conveyance roller 13 of the R / W unit 5 is turned off ( S2 → S3).

  In this state, the non-contact IC tag 61 is close to the R / W unit 5, and the R / W unit 5 reads data from the non-contact IC tag 61.

  A state (read status) indicating whether or not data has been correctly read from the non-contact IC tag 61 is checked (S5). If normal, the sheet is conveyed again by turning on the clutch 15 (S6). As a result, the sheet passes between the cleaning roller 4 and the platen roller 12, and the recording surface of the sheet is cleaned (S7).

  Thereafter, the sheet passes through the heat roller 3 so that the recording surface of the sheet is heated to a predetermined temperature (predetermined temperature of approximately 150 ° C. to 200 ° C.), and the previously recorded image is erased by subsequent cooling. (S8). In addition, by driving the cooling fan 2, heat storage of the paper transport path and the paper is suppressed, and the recording surface of the paper is kept in a predetermined temperature range at the time of image recording by the subsequent thermal head.

Subsequently, when the leading edge of the paper reaches immediately before the head position of the thermal head 1, the thermal head lifting motor 26 is driven to bring the head portion of the thermal head 1 into contact with the paper, and then the thermal head 1 is driven to newly A simple image is recorded (S9).
Further, the sheet is conveyed as it is and discharged to the normal sheet discharge unit 40 (S10).

  If data cannot be read from the non-contact IC tag 61 or if the read data is abnormal, the flapper 52 is raised as indicated by the broken line shown in FIG. 4, and the clutch 15 of the R / W unit is turned on. As a result, the sheet is discharged to the abnormal sheet discharge unit 50 (S5 → S11 → S12 → S13).

  FIG. 8 is a flowchart showing a processing procedure for image recording. As shown in FIG. 4A, when the leading edge of the sheet is detected, the process waits until the thermal head 1 reaches the lowering start position (S21 → S22). When it is time to lower the thermal head 1, the thermal head 1 is lowered and then waits until the print start position is reached (S 23 → S 24). Thereafter, as shown in FIG. 4E, until one end of the sheet is detected, one line of print output is performed, and the remaining print lines are counted in order to count the number of lines until image formation is completed. The counter is subtracted (S25 → S26 → S27 → S28). The processes in steps S25 to S28 are repeated until this counter becomes zero.

  If the end of the sheet is detected, the value of the remaining print line counter is replaced with the number of lines up to the end margin. Further, a detected flag at the end of the sheet is set (S26 → S30).

  When the value of the remaining print line counter becomes 0, the thermal head is raised (S29 → S31).

  In this way, a predetermined image is recorded (printed) on the paper, and the thermal head 1 is prevented from being in contact with the platen roller 10 in the absence of the paper, thereby preventing the thermal head 1 from being damaged.

  FIG. 9 and FIG. 10 show processing procedures from when print data is received from the host computer 101 to when actual printing (image recording) is performed and the paper is discharged. As shown in FIG. 9A, when print data is first received, it is expanded into data for image recording (S41 → S42 → S43 → S41...). When the development for one page is completed, the process waits until it becomes possible to start conveying the sheet on the sheet conveying path (S44). If the paper already started to be fed is transported to a predetermined position, the number (buffer No.) of the paper processing buffer for printing (image recording) of the print data is obtained, and the developed print in the buffer Data is set (S45 → S46). In this example, this buffer has an eight-stage ring buffer structure so that a maximum of eight sheets can be conveyed on the sheet conveyance path.

  FIG. 9B shows a procedure for performing the printing process based on the data set in the buffer as described above. First, the states of all sensors on the paper transport path are read (S51). However, the state of this sensor is read out from the memory which is the result obtained by the interrupt process by the timer interrupt at a constant period. If there is data to be printed at the current timing, printing for one line is performed, and preparation for printing for the next one line is made (S52 → S53 → S54). Subsequently, a buffer number to be processed is acquired from the buffers, and the conveyance of the paper corresponding to the buffer number is confirmed (S55 → S56). This is performed for all buffer numbers (S57 → S55 →...). Step S56 will be described later.

  The above process is repeated until all the sheets are discharged from the sheet conveyance path (S58 → S51 →...).

  FIG. 9C is a diagram showing the processing contents in the timer interruption. The CPU interrupts the CPU in the control circuit 70 at a fixed period by hardware, and the stepping motor 33 is driven by one step by the interrupt processing. Thereafter, the states of all the sensors on the paper transport path are acquired simultaneously, and the memory To store. For example, in the example shown in FIG. 3, [0/1] data of eight sensors 80a to 80h are simultaneously acquired as 8-bit data.

  FIG. 10 is a flowchart showing the processing contents of step S56 shown in FIG. This processing is performed according to the processing phase. For example, if it is “Phase 0”, nothing is processed (S61 → S62). If it is “Phase 1”, it waits for the start of conveyance (S63). If it is "Phase 2", it waits until the sensor 80a passes, that is, until the trailing edge of the preceding paper passes the sensor 80a (S64). Such a phase exists up to “Phase 9”. If these conditions are not satisfied, the processing is terminated as it is (S72). If the condition is satisfied, the phase number is updated to the next phase (S73).

  FIG. 11 shows an example of the phase number corresponding to the position on the paper transport path of the paper to which the data stored in the 8-stage buffer is applied. In the state shown in (A), just as shown in (A) of FIG. 1 is for managing the state of the paper 60d. Since the sensor 80g detects the paper 60d, the phase number is phase 8, and the sensor 80g is waiting for the paper 60d to pass. In addition, the buffer No. 2 is for managing the paper 60c. Since the sensor 80d detects the paper 60c, the phase number is phase 5, and the sensor 80d is waiting for the paper 60c to pass. The same applies to other sheets.

  Thereafter, when the trailing edge of the paper 60c passes the sensor 80d, the state shown in FIG. That is, the buffer No. managing the paper 60c. Phase 2 is a state waiting for the sensor 80e to pass the rear end of the paper 60c, that is, phase 6.

  In this way, the phase number of each buffer changes with time. Since this buffer is used as a ring buffer, the buffer No. If the next sheet starts to be fed after use up to 8, the buffer No. at that time is shown in FIG. 1 is used to manage the newly fed paper.

  In addition to detecting the position of each sheet on the sheet conveyance path, the process when the skew of the sheet is detected as shown in FIG. That's fine. Further, even when a sheet having a length shorter than the specified size is conveyed for some reason, the thermal head does not directly contact the platen roller 10 by the processing shown in FIGS. 1 breakage can be prevented.

It is a figure which shows the structure inside the printing apparatus which concerns on embodiment of this invention, and is sectional drawing of the AA part of FIG. FIG. 2 is a top view illustrating an internal configuration of the printing apparatus. FIG. 6 is a diagram illustrating an example of a positional relationship between a plurality of sensors on a sheet conveyance path and a sheet. It is a figure which shows the example of conveyance of the paper in an image recording part, and the raising / lowering of a thermal head. FIG. 5 is a diagram illustrating an example of a layout on a plane of a plurality of sensors on a paper transport path. FIG. 3 is a block diagram illustrating a configuration of a control unit of the printing apparatus. 3 is a flowchart illustrating an overall processing procedure of a control unit of the printing apparatus. It is a flowchart which shows the process sequence of the image recording in an image recording part. 4 is a flowchart showing processing at the time of receiving print data from a host computer and processing contents accompanying paper conveyance. It is a flowchart which shows the process sequence of step S56 of FIG. FIG. 10 is a diagram illustrating an example of a change in phase number of each buffer accompanying paper conveyance.

Explanation of symbols

1-thermal head 2-cooling fan 3-heat roller 4-cleaning roller 5-R / W unit (non-contact IC tag read / write unit)
6,7-Feeding roller 8,9-Pickup roller 10,11,12-Platen roller 13-Conveying roller 14-Elevating table 15-Clutch 16-Feeding tray 18, 19-Clutch 20, 21-Registration roller 22 ~ 25-Conveying roller 33-Stepping motor 40-Normal paper discharge unit 50-Abnormal paper discharge unit 60-Paper 80-Sensor 100-Print device 101-Host computer

Claims (2)

A paper transport means for transporting the paper to the paper transport path by step driving of a stepping motor;
Image recording means for recording an image on paper conveyed by the paper conveying means;
A sensor for detecting the presence or absence of paper, disposed at a plurality of predetermined positions on the paper transport path;
Sensor state acquisition means for capturing the detection contents of the plurality of sensors at the same time and storing them in a memory after the step driving for each step driving of the stepping motor;
Until the step of the stepping motor proceeds, a sheet processing unit that reads the presence or absence of a sheet at the position of the sensor with reference to the contents of the memory and performs processing according to the position of the sheet;
A printing apparatus comprising:   2. The print according to claim 1, wherein the sheet transport unit and the sensor state acquisition unit are execution units of an interrupt processing program by a CPU, and the sheet processing unit is an execution unit of a program other than the interrupt processing program by the CPU. apparatus.

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